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(NoModeL) J. S. CAMPBELL. ARTIFICIAL TOOTH.

Patented Dec. 22, 1891.

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UNITED STATES P TENT @FFICE.

JOHN S. CAMPBELL, OF LONDON, ENGLAND.

ARTIFICIAL TOOTH.

SPECIFICATION forming part of Letters Patent No. 465,458, dated December22, 1891. Application filed June 9, 1890. Renewed October 27, 1891.Serial No. 409,975. (No model.)

To all whom it may concern:

Be it known that I, JOHN S. CAMPBELL, of

London, England, have invented certain new and useful Improvements inthe Manufacture of Artificial Teeth, of which the following is aspecification, reference being had to the accompanying drawings.

The object of my invention is to improve a porcelain tooth representingahuman tooth, so that it may be more firmly attached tothe metallic plateby soldering, and so that it may have upon the lingualside a morenatural feeling to the tongue of the wearer and be more easily cleanedby brushing or wash ing than ordinary artificial teeth can be.

In the drawings, Figure l is a perspective view of a-metallicmouth-plate having artificial teeth applied to it in accordance with.

my invention. Fig. 2 is a perspective view of a single tooth constructedaccording to my invention with a narrow vertical slot in its lingualside. Fig. 3 is a horizontal sectional view of the tooth illustrated inFig. 2, viewed from the base of the tooth and showing apin crossing thevertical slot and embedded in the tooth structure. Fig. lisa perspectiveview of a countersunk tooth not made in accordance with my invention andhaving a large cavity extending from its lingual side inward and formedby excavating the main of the'tooth structure. This large cavity iscrossed by a pin embedded at its ends in the remaining shell of thetooth, which is illustrated merely to better show by comparison thedistinctive character of my improvements. Fig. 5 is a perspective viewof another countersunk tooth not made in accordance with my invention,but having its main central portion bored out from the base of thetooth, so as to leave a shell and having a headed pin at the bottom ofthe bore embedded in the tooth structure, but projecting into the cavityformed by the bore. This tooth is illustrated for the same purpose asthe tooth shown in Fig. 4, whereby the characteristicmerits of myimprovements more clearly appear. Fig. 6 is a perspective viewillustrating the ordinary way of attaching a porcelain tooth to a goldplate.

Referring to the letters upon the drawings, A in Fig. 1 illustrates adental plate, and B central part teeth secured thereto in accordancewith my invention.

O in-Figs. 2 and 3 indicates a tooth detached and provided with a narrowvertical slot D, preferably tapered or Wedge-shaped, with its widestpart at'E on the lingual side of the tootn. This slot should extend toabout the center of the tooth and is so narrow that it does notmaterially impair the strength of the tooth. Its object is to receive athin metallic vertical backing connected with the plate, so that it willbe substantially at right angles, with the edge of the plate.

P, Fig. 3, indicates a pin, preferably of plati- 6; num, extendingacross the vertical slot, with its ends supported in the toothstructure. This pin is molded into place in the process of forming thetooth by means of formers or molds Well understood in the art of manu-7o factoring porcelain teeth.

According to the usual method of fasten ing porcelain teeth to ametallic plate the gold backing is fastened fiatwise to the plate on thelingual side of the teeth to two platinum pins a a, Fig. 6, projectingfrom the teeth. The result is that the backing is sub stantially a thinfiat extension of the plate upon the lingual side of the teeth. As thestrain upon the teeth in use is forward and backward or in the directionof the outer and inner faces of the teeth, it will be perceived that bythe ordinary method the backing is applied in such relation to the teethand plate as to present the least resistance to bending or displacementof the teeth. As the proximal sides of the teeth are in contact, theteeth are self-supporting there. Besides, very little strain occurs inthe direction of the row of teeth, it being ordinarily across the row.The attachment of artificial teeth to a metallic plate by the old methodis therefore 'weak and insecure to resistthe only strain they are liableto suffer. Besides this, another objection to it is that. it gives anunnatural and unpleasant feeling when the tongue of the wearer comes incontact with the lingual sides of the teeth. Another and still greaterobjection is that the ordinary backing usually covers not only thelingual 10o sidesof the teeth, but also the lower parts of the spacesbetween the teeth upon the lingual sides, thus making it very difficultto cleanse them. Consequently matteraccumulates between the teeth on thelingual side around and under the edges of the backing and becomesoffensive, and it is difficult, if not impossible, for the wearer todislodge it. By my improvements a thin plate of suitable mate rial toform a backing for each tooth is set into the tooth, so that the strainis always edgewise and never sidewise upon the backing. I thus securethe greatest strength possible in a tooth-backing, and at the same timeI reduce the quantity of material used in the backing to the minimum.Besides this, I preserve a natural contour on the lingual side of eachtooth and avoid exposing any edges of the backing. around and behindwhich it is possible formatter to accumulate and become foul andoffensive.

In Fig. 4 is shown a tooth countersunk from the lingual side and reducedto a shell by-exeavation and provided With a pin crossing the excavationand lodged at its opposite ends in the shell of the tooth. This form oftooth I have been recently advised has been made to be connected bymeans of rubber to the plate; but it would not serve the purpose of myinvention. In the first, place, such alarge cavity would require toomuch gold to till it. In the second place, if filled with metallicsolder, it would be insecure, because the contraction and expansion ofthe metal in so large a vol- 11 me being unequal to the contraction andexpansion of the porcelain shell would be liable to crack the shell orto destroy its fitting within the-shell, or both.

The principle of my invention is to employ a thin backing edgewise inthe narrow vertical slot in the body of the tooth substantially at rightangles to the general surface of the plate to which it is attached,whereby the greatest resistance to strain upon the tooth is secured withthe least possible amount of metal and without projections from thelingual side of the tooth or any extended metallic surface there to comein contact with the tongue.

Fig. 5 shows a tooth, also known asacountersunk tooth, bored out at itsbase with a large opening and provided with a headed pin in the centerof the bottom of the bore, with the head projecting into the bore. The

object of this is to receiye a volume of rubberwith a plate, whichbacking has its edges substantially at right angles with the edge of theplate Where it is applied, in combination with a pin crossing said slotand having its opposite ends bearing in the tooth structure,substantially as set forth.

In testimony of all which I have hereunto subscribed my name.

JOHN S. CAMPBELL.

\Vitnesses:

S. G. HOPKINS, LoUIs G. J ULIHN.

